Sunday, January 31, 2010

Introduction To System Development/Software Life Cycle Models

The trends of increasing technical complexity of the systems, coupled with the need for repeatable and predictable process methodologies, have driven System Developers to establish system development models or software development life cycle models.
Nearly three decades ago the operations in an organization used to be limited and so it was possible to maintain them using manual procedures. But with the growing operations of organizations, the need to automate the various activities increased, since for manual procedures it was becoming very difficult, slow and complicated. Like maintaining records for a thousand plus employees company on papers is definitely a cumbersome job. So, at that time more and more companies started going for automation.

Since there were a lot of organizations, which were opting for automation, it was felt that some standard and structural procedure or methodology be introduced in the industry so that the transition from manual to automated system became easy. The concept of system life cycle came into existence then. Life cycle model emphasized on the need to follow some structured approach towards building new or improved system. There were many models suggested. A waterfall model was among the very first models that came into existence. Later on many other models like prototype, rapid application development model, etc were also introduced.

System development begins with the recognition of user needs. Then there is a preliminary investigation stage. It includes evaluation of present system, information gathering, feasibility study, and request approval. Feasibility study includes technical, economic, legal and operational feasibility. In economic feasibility cost-benefit analysis is done. After that, there are detailed design, implementation, testing and maintenance stages.

In this session, we'll be learning about various stages that make system's life cycle. In addition, different life cycles models will be discussed. These include Waterfall model, Prototype model, Object-Oriented Model, spiral model and Dynamic Systems Development Method (DSDM).
LESSON 29

Introduction to System Analysis and Design



29.1 INTRODUCTION

Systems are created to solve problems. One can think of the systems approach as an organized way of dealing with a problem. In this dynamic world, The subject System Analysis and Design, mainly deals with the software development activities.

29.2 OBJECTIVES

After going through this lesson, you should be able to:

understand a system
understand the different phases of system developments life cycle
know the components of system analysis
know the components of system designing
29.3 Defining A System

A collection of components that work together to realize some objective forms a system. Basically there are three major components in every system, namely input, processing and output.





In a system the different components are connected with each other and they are interdependent. For example, Human body represents a complete natural system. We are also bound by many national systems such as political system, economic system, educational system and so forth. The objective of the system demand that some output is produced as a result of processing the suitable inputs.

29.4 SYSTEM LIFE CYCLE

System life cycle is an organisational process of developing and maintaining systems. It helps in establishing a system project plan, because it gives overall list of processes and sub-processes required developing a system.

System development life cycle means combination of various activities. In other words we can say that various activities put together are referred as system development life cycle. In the System Analysis and Design terminology, the system development life cycle means software development life cycle.

Following are the different phases of software development cycle:

System study
Feasibility study
System analysis
System design
Coding
Testing
Implementation
Maintenance



sumber dari http://www.nos.org/htm/sad1.htm